Ox 66 smoking bad

[Antnylsu]

We also drained the vst and hooked up an external gas tank to make it sure none of the symptons are fuel related. No change.

[Antnylsu]

We took another look at the oil pump o ring and decided to change the o ring since it was $10 part. The yamaha service tech suggested fuel pumps first and then suggested a whole new oil pump after I told him the pumps were brand new. Are these known to go bad? I have heard of the linkage rod breaking but not the pump. Looking for feedback before I drop more money on another part.

[rodbolt17]

I have seen the pump shft seal fail.
typically the bottom 2 cyl will show excessive oil.

[Antnylsu]

We changed the seal on the shaft and the one between the block and pump. The service tech we are dealing with is loaning a spare oil pump to try.

[Antnylsu]

We took the boat out last weekend and both motors drank oil. We burned 160 gallons of gas and 7 gallons of oil between the two. That is roughly 22:1 ratio. Is there any way to test the oil pumps?

[99yam40]

service manual should give the test procedure and the amount of CCs measured at certain RPMs over a certain time period

Make sure you run it on premix while measuring oil out put

[tsheehy]

Any chance the engine mounted oil tank is overflowing and the excess oil is getting drained into the air cover and sucked back into the engine?

-- Tom

[Antnylsu]

It has been hard for me to find time to finish this repair, but had a chance to swap out the oil pumps last weekend. It was the seal on the pump shaft that was causing the issue. I had previously replaced the o-ring that goes between the cranckcase and the oil pump, but it turned out to be the pump itself. It was evident when I took the pump off the block and there was a bunch of oil coming out of the cranckcase. After replacing the oil pump, the smoke is now a normal amount and burning approximately 60:1 on a trip with a bunch of idling.